HR: 0800h
AN: C41A-0063    [Abstracts]
TI: Increasing Wastage of the Bering and Malaspina Glacier Systems, Alaska-Yukon, 1972 to 2006
AU: * Muskett, R R
EM: rmuskett@iarc.uaf.edu
AF: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775-7320, United States
AU: * Muskett, R R
EM: rmuskett@iarc.uaf.edu
AF: International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK 99775- 7340, United States
AU: Lingle, C S
EM: clingle@gi.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775-7320, United States
AU: Sauber, J M
EM: Jeanne.M.Sauber-Rosenberg@nasa.gov
AF: NASA Goddard Space Flight Center, NASA/GSFC Code 698, Greenbelt, MD 20771, United States
AU: Tangborn, W V
AF: HyMet, Inc., 19001 Vashon Hwy, SW, Suite 201, Vashon, WA 98070, United States
AU: Rabus, B T
AF: MacDonald, Dettwiler and Associates, Ltd, 13800 Commerce Parkway, Richmond, BC V6V 2J3, Canada
AU: Echelmeyer, K A
AF: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775-7320, United States
AB: Ice dynamics are integral to the net mass balances of the huge Bagley-Bering and Seward-Malaspina Glacier systems of south-central Alaska. Quasi-periodic surging of the main trunks and some large tributaries of these exceptionally active glacier systems are important contributors to their increasing volume losses in the present rapidly-warming climate, because surges rapidly transport ice from higher elevations, where it is "safe," to lower elevations where it subject to increased ablation. New estimates of mass losses from the Bering and Malaspina Glacier systems during 1972-2006 were derived from analysis of (i) digital elevation models (DEMs) synthesized from airborne and spaceborne interferometric synthetic aperture radar (InSAR); (ii) small-aircraft laser altimetry; and (iii) spaceborne laser altimetry acquired by ICESat. Adjustments for estimated seasonal snow accumulation were applied to datasets acquired at times subsequent to late summer. Adjustments for systematic DEM biases were also applied. The area-average lowering rate on the main-trunk of the Bering Glacier system from 1972 to 1995 was 0.9 ± 0.1 m/yr. The major 1993 to ‘95 surge moved ice rapidly from the surge reservoir into the piedmont lobe where rapid surface melting was facilitated by the heavily crevassed surface. The lowering rate accelerated to 3.0 ± 0.1 m/yr during 1995 to 2000, then moderated to 1.4 ± 0.1 m/yr during 2000 to 2003. On the Malaspina Glacier system, the area-average rate of surface lowering was 1.4 ± 0.1 m/yr during 1972 to 1999. It then increased by 30% to 1.8 ± 0.1 m/yr during 1999 to 2002. Near-concurrent surges of Agassiz Glacier (a west piedmont lobe tributary), lower Seward Glacier (main source for the central Seward lobe), and Marvine Glacier (a detached former tributary of the eastern piedmont lobe) were observed during this 3-year time span of increased surface lowering. Recent ICESat-derived elevation changes from 2003 to 2006 indicate increasing wastage on the Malaspina piedmont lobe. By contrast, its main accumulation area, upper Seward Glacier, which was drawn down by the 1999-2002 surge, is showing recovery with increasing surface elevations. Concurrently, elevations on Bagley Ice Valley are also increasing in preparation, evidently, for the next surge of the Bering Glacier system. For both of these large glacier systems we estimate a combined volume loss of 254.0 ± 16.5 km³ (water equivalent) over an area of 7734 km² during 1972 to 2003, representing over 80% and 70% of the areas of the Bering and Malaspina Glacier systems, respectively. This is equivalent to a mean surface lowering of 31 to 35 meters. These glaciers are making an increasing contribution to globally-rising sea-level.
DE: 0720 Glaciers
DE: 0762 Mass balance (1218, 1223)
DE: 1621 Cryospheric change (0776)
DE: 1640 Remote sensing (1855)
SC: Cryosphere [C]
MN: 2007 Fall Meeting